1. Field of the Invention
The present invention is an improved sundial with improvements relating to versatility and ease of manufacture, installation and use.
2. Description of the Prior Art
Sundials indicating local apparent time have been used for thousands of years. Sundials indicating civil or mean time were invented by Christian in 1884 (U.S. Pat. No. 303,118) and by Crehore in 1905 (U.S. Pat. No. 794,787). These inventions used a bead or ball as a gnomon to make a symetrical shadow on a cylindrical surface with time lines corrected for the equation of time. No provision was made to correct for the difference between local and zone time.
To indicate zone time, a one minute time correction is required for each 15 minutes of longitude the site meridian is displaced from the time zone meridian. Recent inventions with corrections for the difference between local and zone time require extensive precise fabrication or casting, and expert installation adjustment and use. Some require custom manufacture for the site latitude. It has long been known that a proper sundial at one location can be set to indicate the correct time at a second location.
Also recently instruments have been developed for sighting the site "solar window" and determining the times the sun's rays will be obstructed at the site. These instruments have either been very complex or very general and inaccurate.